A communication system such as long term evolution (LTE) system, etc, may operate in time division duplexing (TDD) mode, i.e., an uplink (UL) and a downlink (DL) may adopt different time slots of a same frequency. A LTE TDD system may allocate an uplink-downlink configuration (Uplink-Downlink Configuration) in a semi-static manner according to a service type, to meet requirements of different services asymmetrical in terms of the uplink and the downlink.
At present, the LTE TDD system defines 7 uplink-downlink configurations in all. As shown in Table 1, “D” represents a downlink subframe, “U” represents an uplink subframe, and “S” represents a special subframe. Referring to Table 1, in each uplink-downlink configuration, a proportion of time domain resources reserved for a downlink service to the total resources ranges from 40% to 90%. As shown in Table 1, an uplink-downlink switching periodicity (i.e., uplink-downlink configuration periodicity) includes 5 ms and 10 ms. In a configuration periodicity of 5 ms, a wireless frame includes two special subframes, i.e., a subframe 1 and a subframe 6. In a configuration periodicity of 10 ms, a wireless frame includes only one special subframe, i.e., a subframe 1.
TABLE 1Index ofUplink-downlinkConfigurationSubframe numberconfigurationperiodicity01234567890 5 msDSUUUDSUUU1 5 msDSUUDDSUUD2 5 msDSUDDDSUDD310 msDSUUUDDDDD410 msDSUUDDDDDD510 msDSUDDDDDDD6 5 msDSUUUDSUUD
In an islanding cell or a cell covered by a low-power node, an inter-cell interference has a little effect on the cell. Traffic burst in the uplink and the downlink may have a great effect in a cell which serves a small amount of users. If the uplink-downlink configuration may be adjusted adaptively according to the requirement of uplink-downlink traffic, TDD system may be operated to advantage by using the spectrum resources effectively.
To provide flexibility, a method for adjusting dynamically uplink-downlink configuration is provided. In the method, some flexible subframes may by set in a system, and each flexible subframe in the wireless frame may be configured dynamically to be an uplink subframe or a downlink subframe. FIG. 1-a is a schematic diagram showing a dynamic TDD subframe configuration in a wireless frame, i.e., subframes 3, 4, 8 and 9 in the wireless frame may be flexible subframes.
Furthermore, if the uplink-downlink configuration has a configuration periodicity which may switch between 5 ms and 10 ms, subframes 3, 4, 7, 8 and 9 in the wireless subframe may be configured to be flexible subframes, as shown in FIG. 1-b. In practical communication, a type of the subframe 6 is determined from the usage of the subframe 7. If the subframe 7 is used for the uplink transmission, the subframe 6 may be a special subframe, which is configured to switch a transmission from the downlink to the uplink. If the subframe 7 is configured for downlink transmission, the subframe 6 may be a downlink subframe.
In practice, in some application scenarios that the uplink-downlink configuration has a configuration periodicity which may dynamically switch between 5 ms and 10 ms, data receiving errors may sometimes occur to some user terminals, when the user terminal receives data carried in the subframe 6 of a wireless frame.